New research outlines just how hard life was for dinosaurs brave enough to venture into rainforests near the equator.
In these regions, only a few species of small-bodied carnivorous dinosaurs survived, the National Science Foundation reported. A recent study may explain this phenomenon by showing rainforest climates over 200 million years ago fluctuated rapidly and were characterized by periods of intense drought and heat. Wildfires were also frequent in the regions, which reshaped local vegetation.
"Our data suggest it was not a fun place," said scientist Randall Irmis of the University of Utah. "It was a time of climate extremes that went back and forth unpredictably. Large, warm-blooded dinosaurian herbivores weren't able to exist close to the equator--there was not enough dependable plant food."
The earliest-known dinosaur discovered in Argentina date back to about 230 million years ago, and within 15 million years of that the local population started to rapidly change in most regions excluding tropical latitudes. The selective population of small meat-eaters found in these regions persisted for about 30 million years after the first dinosaurs appeared.
The researchers made their findings by looking at: fossils, charcoal from ancient wildfires, isotopes in organic matter, and carbonate nodules born in ancient soil. The findings revealed that in tropical regions, pseudosuchian archosaurs (the first alligators and crocodiles) outnumbered dinosaurs significantly, and dinosaurs made up less 15 percent of vertebrate animal remains.
The study, which focused on fossils from Ghost Ranch in northern New Mexico, could have implications for the future of Earth's climate. During this early era in history, atmospheric carbon dioxide levels were between four and six times what they are today.
If we continue along our present course, similar conditions in a high-CO2 world may develop, and suppress low-latitude ecosystems," Irmis said.
The findings were published in a recent edition of the journal Proceedings of the National Academy of Sciences (PNAS).
